210 



ZOOLOGY 



plates are shorter than the others, and at their bases arise elongated processes 

 called auricles (aur.), which bear swimming-plates. The meridional canals (mdr. c) 

 unite with one another, and, with the cesophageal canals, are continued into the 

 lappets, where they become curiously coiled. The principal tentacles are 

 usually absent in the adult, but are represented by their basal portions, which 



mnd.c 



FIG. 156. Deiopea kaloknenota. A, adult ; B. young, aur. auricle ; lp. lappet ; I. t. lateral 

 tentacles ; mrd. c. meridional canal ; mth. mouth. (After Chun.) 



are small, situated at the oral end, and devoid of sheaths. From each tentacle- 

 base grooves are continued along the oral surface to the auricles, and from the 

 grooves depend numerous small lateral tentacles (l.t.). In the young condition 

 the Lobata resemble such compressed Cydippida as Euchlora, having a pair of 

 long principal tentacles, no lappets, and unbranched vessels (B). 



The Cevtida are represented by the remarkable " Venus's Girdle" (Cestus 

 venerw), a band-shaped Ctenophore (Fig. 157) which sometimes attains a length 

 of 1^ metre, or nearly 5 feet. The body is greatly elongated horizontally in the 



\ 



Jiiitfii^ 



B 



FIG. 157. Cestus veneris. A, adult, B. young. /. t. lateral tentacles ; ,,dk. mouth; .<. 

 s. pi: swimming-plates ; t. tentacle. (After Chun.) 



vertical, and compressed in the transverse, plane, so as to have the form of a 

 ribbon, which progresses by undulations of the whole body as well as by the 

 action of its swimming-plates. Four of the swimming-plates (8. pi. 1 ) are very 

 small ; the other four (.pl. 2 ) are continued all along the aboral edge of the body. 

 The bases of the two principal tentacles (t. ) are large and are enclosed in sheaths, 

 and, as in Lobata, numerous small lateral tentacles (l.t. ) spring from grooves. 



